title: Fibrils connect microtubule tips with kinetochores: a mechanism to couple tubulin dynamics to chromosome motion.
abstract: Kinetochores of mitotic chromosomes are coupled to spindle microtubules in ways that allow the energy from tubulin dynamics to drive chromosome motion. Most kinetochore-associated microtubule ends display curving "protofilaments," strands of tubulin dimers that bend away from the microtubule axis. Both a kinetochore "plate" and an encircling, ring-shaped protein complex have been proposed to link protofilament bending to poleward chromosome motion. Here we show by electron tomography that slender fibrils connect curved protofilaments directly to the inner kinetochore. Fibril-protofilament associations correlate with a local straightening of the flared protofilaments. Theoretical analysis reveals that protofilament-fibril connections would be efficient couplers for chromosome motion, and experimental work on two very different kinetochore components suggests that filamentous proteins can couple shortening microtubules to cargo movements. These analyses define a ring-independent mechanism for harnessing microtubule dynamics directly to chromosome movement.
authors.affiliation: Department of M.C.D. Biology, University of Colorado, Boulder, CO 80309-0347, USA. richard.mcintosh@colorado.edu
authors.forename: J Richard
authors.initials: JR
authors.lastname: McIntosh
authors.forename: Ekaterina L
authors.initials: EL
authors.lastname: Grishchuk
authors.forename: Mary K
authors.initials: MK
authors.lastname: Morphew
authors.forename: Artem K
authors.initials: AK
authors.lastname: Efremov
authors.forename: Kirill
authors.initials: K
authors.lastname: Zhudenkov
authors.forename: Vladimir A
authors.initials: VA
authors.lastname: Volkov
authors.forename: Iain M
authors.initials: IM
authors.lastname: Cheeseman
authors.forename: Arshad
authors.initials: A
authors.lastname: Desai
authors.forename: David N
authors.initials: DN
authors.lastname: Mastronarde
authors.forename: Fazly I
authors.initials: FI
authors.lastname: Ataullakhanov
mesh_terms: D000818:Animals; D002460:Cell Line; D002875:Chromosomes / Q000378:metabolism* / Q000648:ultrastructure; D003599:Cytoskeleton / Q000378:metabolism / Q000648:ultrastructure; D018386:Kinetochores / Q000378:metabolism* / Q000648:ultrastructure; D008870:Microtubules / Q000378:metabolism* / Q000648:ultrastructure; D048328:Potoroidae; D008941:Spindle Apparatus / Q000378:metabolism / Q000648:ultrastructure; D014404:Tubulin / Q000378:metabolism
chemical_list: D014404:Tubulin